Effect of coating thickness on interfacial shear behavior of zirconia-coated sapphire fibers in a polycrystalline alumina matrix

The effect of zirconia (ZrO₂) interfacial coatings on the interfacial shear behavior in sapphire reinforced alumina has been examined via loaded sol dipping technique and then hot pressing. Interfacial shear strength and sliding behavior of the coated fibers are also examined via thin-slice indentation fiber pushout and pushback techniques. The high interfacial shear strengths and sliding stresses measured, as well as the potentially strength degrading surface reconstruction observed on the coated fibers after hot pressing and heat treatment, indicate that dense zirconia coatings are not suitable candidates for optimizing composite toughness and strength in the sapphire fiber reinforced alumina system.